Questions and answers

What is a hot gas valve?

What is a hot gas valve?

The hot gas bypass is a valve that automatically regulates the cooling temperature in the dryer exchanger based on the refrigerant pressure. The pressure measured after the heat exchanger directly correlates to the temperature in the system. A low pressure means there will be a low temperature.

Is hot gas bypass the same as hot gas reheat?

HOT GAS REHEAT uses the high pressure, high temperature, compressor discharge gas to reheat the air leaving the evaporator coil. HOT GAS BYPASS provides an artificial load on the evaporator by introducing a portion of high pressure, high temperature gas to the evaporator/suction side of the system.

What is hot gas discharge?

Hot gas bypass (also called discharge bypass) is a feature in a refrigeration system uses to satisfy the mechanical needs of the system during low load conditions.

How do you adjust a hot gas valve?

By turning the adjustment stem counterclockwise one complete turn, the pressure setting will decrease approximately 4 psig. Using an adjustable wrench, remove the cap that covers the adjustment stem of the valve. Make sure to adjust in small increments allowing the system to stabilize between adjustments.

Why is hot gas bypass used?

Hot gas bypass can stabilize the system balance point by diverting hot, high-pressure refrigerant vapor from the discharge line directly to the low- pressure side of the system. This tactic reliable operation by introducing problems stemming from insufficient oil return and refrigerant logging in the HGBP line.

What is a false load?

Hot gas bypass valves are a simple and very effective way to add a false load on an evaporator coil. By adding hot gas from the discharge line into the evaporator, we can increase the evaporator pressure and temperature. Because this load is not put there by heat from the return air, the load is referred to as false.

Is hot gas reheat energy recovery?

Hot-gas reheat is a common type of heat recovery often employed in dedicated outside-air systems (DOAS).

What is hot gas bypass used for?

What does a hot gas bypass valve do?

Is the refrigeration process open or closed?

From our definition, the refrigeration cycle is an open or closed system (the above figure is a closed system), where refrigerant passes through. The refrigeration cycle begins at the compressor which compresses the refrigerant from a low temperature, low-pressure vapor into a high pressure high-temperature gas.

What is the purpose of hot gas bypass?

What does a reheat valve do?

Actuation of the reheat is accomplished by energizing a valve that allows refrigerant hot gas to flow through the hot gas reheat coil. Dehumidification is allowed only when the outside air temperature is above 40F or below 100F. Dehumidification is not allowed if there is an active call for heating .

What happens when you open the hot gas bypass valve?

The hot gas bypass valve opens putting a false load on the evaporator, since the evaporator temperature has been increased, the supply air serving the lecture hall will also be increased preventing set point to be reached. As people re-enter the hall, a true load will increase evaporator temperature and the hot gas bypass will close.

When to use hot gas bypass in an air conditioner?

Hot gas bypass is recommended when the load on an evaporator varies and operation of the air conditioning system is desired at lower than design conditions. Additionally, hot gas bypass is used when the evaporator coil is designed for comfort cooling (latent and sensible loads) versus precision cooling (all sensible loading).

What happens when hot gas is added to an evaporator?

As a space or process temperature reaches set point, hot gas can be added to the evaporator to raise its temperature. With increased evaporator temperature, set point will take longer to achieve, thus increasing compressor run times all the while preventing evaporator freeze up.

How is a cold gas thruster different from a rocket engine?

A cold gas thruster (or a cold gas propulsion system) is a type of rocket engine which uses the expansion of a (typically inert) pressurized gas to generate thrust. As opposed to traditional rocket engines, a cold gas thruster does not house any combustion and therefore has lower thrust and efficiency compared…